SpaceX’s sort-of-top-secret Zuma mission for the U.S. government—which presumably has nothing to do with the South African president of the same name—may or may not go ahead on Friday evening, after delays made its planned Thursday launch impossible.

According to documents obtained by Wired last month, the Zuma mission involves carrying a Northrop Grumman-made satellite into low-Earth orbit for the U.S. government. That’s pretty much all we know about it—it’s not even apparent which government branch or agency is the client here.

Elon Musk’s firm was originally supposed to launch the Zuma payload on Thursday evening. However, SpaceX said in a couple of tweets that it was delaying the launch so it could more closely look at component-test data relating to another mission.

It still has a slot for Friday evening but will take as long as it needs to examine the data.

Specifically, the company is looking at data relating to the nose cone—known as “fairing”—that protects the payload. The Zuma mission’s fairing will be jettisoned to expose the satellite once SpaceX’s Falcon 9 clears the Earth’s atmosphere.

Standing down on Zuma mission to take a closer look at data from recent fairing testing for another customer.

Northrop Grumman(noc) is itself in the process of buying a spaceflight firm called Orbital ATK, which serves the International Space Station and will bring the weaponry and aerospace giant into competition with SpaceX.

A SpaceX delivery of a satellite for Israel’s Space Communications went horribly wrong last year after the Falcon 9 rocket exploded. However, SpaceX signed a new deal with the Israeli company last month to launch another two satellites into orbit.

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